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  • Implementing prototypes OR instantiating class objects

    - by intuited
    I'm wondering how to implement prototypal inheritance in Python. It seems like the way to do this would be to either use a metaclass to cause instantiations to actually be classes, rather than objects, or use some magical powers to transform an existing object into a class. The second method would seem to be more flexible, in that it could be applied to existing objects of varied types, while the first would likely be more convenient for typical use cases. Insights on the practicality of these two approaches, as well as alternative suggestions, are hereby requested.

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  • Add objects to NSMutableArray

    - by iorf
    I'm trying to add objects to NSMutableArray (categoriasArray), but its not done by the iterator: @synthesize categoriasArray; for (int i = 0; i < [categories count]; i++) { categoria *cat = [[categoria alloc] initWithDictionary:[categories objectAtIndex:i]]; [self.categoriasArray addObject:cat]; cat=nil; } After the for iterator, categoriasArray has 0 objects. Many thanks

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  • What's the best way to store custom objects in relational database?

    - by user342610
    I have my objects with their properties. Objects could change their structure: properties may be added/removed/changed. Objects could be absolutely dropped. So object's metadata (description, classes, call them like you want :) )could be changed. The database should store objects schemas and instances of these objects. What's the best way to organise a relational database structure to store data mentioned above? Currently I see only two ways: 1) Store objects schemas in a few tables: schema general data,schema properties, possible properties types. Store instances in their tables: instance general data, a few tables - per each type from possible properties types table to store instance properties data. And so on. 2) store objects schemas like in p1 but store instances like XML files in one table: one table for general instance info and one table with instance XML. please, don't ask why/for what I need this. Just need to store custom objects and DB should work fast :)

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  • C++ Expose Already Existing Instance of Objects to a Scripting Language

    - by user947871
    So, I want to be able to modify already instanced C++ objects in a scripting language. I have been looking at Lua with LuaBind and Python with SWIG or Boost::Python, but all I see is how to make new instances of the objects, but I want to modify already existing ones. Example: C++: Player playerOne = new Player(); Scripting Language : playerOne.Transform.x += 5; Is this possible, and if so, wat would you suggest as a good Language/library to achieve this with?

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  • troubles creating a List of doubles from a list of objects

    - by Michel
    Hi, i have a list with objects. The object has a property 'Sales' which is a string. Now i want to create a list of doubles with the values of all objects' 'Sales' properties. I tried this: var tmp = from n in e.Result select new{ Convert.ToDouble ( n.Sales) }; but this gives me this error: Error 106 Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access.

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  • Removing "duplicate objects"

    - by keruilin
    Let's say I have an array of objects from the same class, with two attributes of concern here: name and created_at. How do I find objects with the same name (considered dups) in the array, and then delete the duplicate record in the database. The object with the most-recent created_at date, however, is the one that must be deleted.

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  • Inkscape: what are "line" objects?

    - by Peter Mortensen
    What is a "line" object in Inkscape? Drawing lines in Inkscape is by using the tool "Draw Bezier curves and straight lines (Shift+F6)". This creates objects of another type, "path". Using Inkscape: is there a way to convert an object of type "line" into an object of the more general type "path"? I have imported a drawing (mostly lines, rectangles and text) that has been through Adobe Illustrator: originally made in Inkscape, imported into Illustrator, edited, saved from Illustrator as SVG, imported into Inkscape. Sample from the imported SVG file: <path id="path5855" stroke="#000000" d=" M320.198,275.935" /> <line fill="none" stroke="#000000" x1="348.553" y1="45.097" x2="348.553" y2="185.346" id="line3368" /> Update 1: I have inspected the original XML (SVG) file from 2006 and it does not contain any "line" XML tags. Thus it must be a crime of Adobe Illustrator. When a line is selected in this imported SVG file the bottom panel displays: "Line in root. Click selection to toggle scale/rotation handles.". When a line is selected that was drawn in Inkscape the bottom panel displays: "Path (2 nodes) in Layer 1. Click selection to toggle scale/rotation handles." What is the difference between "line" and "path"? Is "line" some kind of read-only/non-editable object? A generic term like "line" is not easy to use in search, but I have now found the definitions for "line" and "path": SVG line: http://www.w3schools.com/svg/svg_line.asp SVG path: http://www.w3schools.com/svg/svg_path.asp Platform: Inkscape v0.46 (2008-03-10), Windows XP 64 bit, 8 GB RAM.

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  • How to populate a generic list of objects in C# from SQL database

    - by developr
    I am just learning ASP.NET c# and trying to incorporate best practices into my applications. Everything that I read says to layer my applications into DAL, BLL, UI, etc based on separation of concerns. Instead of passing datatables around, I am thinking about using custom objects so that I am loosely coupled to my data layer and can take advantage of intellisense in VS. I assume these objects would be considered DTOs? First, where do these objects reside in my layers? BLL, DAL, other? Second, when populating from SQL, should I loop through a data reader to populate the list or first fill a data table, then loop through the table to populate the list? I know you should close the database connection as soon as possible, but it seems like even more overhead to populate the data table and then loop through that for the list. Third, everything I see these days says use Linq2SQL. I am planning to learn Linq2SQL, but at this time I am working with a legacy database that doesn't have foreign keys setup and I do not have the ability to fix it atm. Also, I want to learn more about c# before I start getting into ORM solutions like nHibernate. At the same time I don't want to type out all the connection and SQL plumbing for every query. Is it ok to use the Enterprise DAAB for now?

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  • qsort on an array of pointers to Objective-C objects

    - by ElBueno
    I have an array of pointers to Objective-C objects. These objects have a sort key associated with them. I'm trying to use qsort to sort the array of pointers to these objects. However, the first time my comparator is called, the first argument points to the first element in my array, but the second argument points to garbage, giving me an EXC_BAD_ACCESS when I try to access its sort key. Here is my code (paraphrased): - (void)foo:(int)numThingies { Thingie **array; array = malloc(sizeof(deck[0])*numThingies); for(int i = 0; i < numThingies; i++) { array[i] = [[Thingie alloc] initWithSortKey:(float)random()/RAND_MAX]; } qsort(array[0], numThingies, sizeof(array[0]), thingieCmp); } int thingieCmp(const void *a, const void *b) { const Thingie *ia = (const Thingie *)a; const Thingie *ib = (const Thingie *)b; if (ia.sortKey > ib.sortKey) return 1; //ib point to garbage, so ib.sortKey produces the EXC_BAD_ACCESS else return -1; } Any ideas why this is happening?

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  • Web Workers - Transferable Objects for JSON

    - by kclem06
    HTML 5 Web workers are very slow when using worker.postMessage on a large JSON object. I'm trying to figure out how to transfer a JSON Object to a web worker - using the 'Transferable Objects' types in Chrome, in order to increase the speed of this. Here is what I'm referring to and appears it should speed this up quite a bit: http://updates.html5rocks.com/2011/12/Transferable-Objects-Lightning-Fast I'm having trouble finding a good example of this (and I don't believe I want to use an ArrayBuffer). Any help would be appreciated. I'm imagining something like this: worker = new Worker('workers.js'); var large_json = {}; for(var i = 0; i < 20000; ++i){ large_json[i] = i; large_json["test" + i] = "string"; }; //How to make this call to use Transfer Objects? Takes approx 2 seconds to serialize this for me currently. worker.webkitPostMessage(large_json);

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  • How to persist objects between requests in PHP

    - by SztupY
    I've been using rails, merb, django and asp.net mvc applications in the past. What they have common (that is relevant to the question) is that they have code that sets up the framework. This usually means creating objects and state that is persisted until the web server is recycled (like setting up routing, or checking which controllers are available, etc). As far as I know PHP is more like a CGI script that gets compiled to some bytecode each time it's run, and after the request it's discarded. Of course you can have sessions, to persist data between requests from the same user, and as I see there are extensions like APC, with which you can persist objects between requests at the server level. My question is: how can one create a PHP application that works like rails and such? I mean an application that on the first requests sets up the framework, then on the 2nd and later requests use the objects that are already set up. Is there some built in caching facility in mod_php? (for example that stores the compiled bytecode of the executed php applications) Or is using APC or some similar extensions the only way to solve this problem? How would you do it? Thanks.

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  • Advantages/Disadvantages of different implementations for Comparing Objects using .NET

    - by Kevin Crowell
    This questions involves 2 different implementations of essentially the same code. First, using delegate to create a Comparison method that can be used as a parameter when sorting a collection of objects: class Foo { public static Comparison<Foo> BarComparison = delegate(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); }; } I use the above when I want to have a way of sorting a collection of Foo objects in a different way than my CompareTo function offers. For example: List<Foo> fooList = new List<Foo>(); fooList.Sort(BarComparison); Second, using IComparer: public class BarComparer : IComparer<Foo> { public int Compare(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); } } I use the above when I want to do a binary search for a Foo object in a collection of Foo objects. For example: BarComparer comparer = new BarComparer(); List<Foo> fooList = new List<Foo>(); Foo foo = new Foo(); int index = fooList.BinarySearch(foo, comparer); My questions are: What are the advantages and disadvantages of each of these implementations? What are some more ways to take advantage of each of these implementations? Is there a way to combine these implementations in such a way that I do not need to duplicate the code? Can I achieve both a binary search and an alternative collection sort using only 1 of these implementations?

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  • Why aren't my objects sorting with sortedArrayUsingDescriptors?

    - by clozach
    I expected the code below to return the objects in imageSet as a sorted array. Instead, there's no difference in the ordering before and after. NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:@"imageID" ascending:YES]; NSSet *imageSet = collection.images; for (CBImage *image in imageSet) { NSLog(@"imageID in Set: %@",image.imageID); } NSArray *imageArray = [[imageSet allObjects] sortedArrayUsingDescriptors:(descriptor, nil)]; [descriptor release]; for (CBImage *image in imageArray) { NSLog(@"imageID in Array: %@",image.imageID); } Fwiw, CBImage is defined in my core data model. I don't know why sorting on managed objects would work any differently than on "regular" objects, but maybe it matters. As proof that @"imageID" should work as the key for the descriptor, here's what the two log loops above output for one of the sets I'm iterating through: 2010-05-05 00:49:52.876 Cover Browser[38678:207] imageID in Array: 360339 2010-05-05 00:49:52.876 Cover Browser[38678:207] imageID in Array: 360337 2010-05-05 00:49:52.877 Cover Browser[38678:207] imageID in Array: 360338 2010-05-05 00:49:52.878 Cover Browser[38678:207] imageID in Array: 360336 2010-05-05 00:49:52.879 Cover Browser[38678:207] imageID in Array: 360335 ... For extra credit, I'd love to get a general solution to troubleshooting NSSortDescriptor troubles (esp. if it also applies to troubleshooting NSPredicate). The functionality of these things seems totally opaque to me and consequently debugging takes forever.

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  • function objects versus function pointers

    - by kumar_m_kiran
    Hi All, I have two questions related to function objects and function pointers, Question : 1 When I read the different uses sort algorithm of STL, I see that the third parameter can be a function objects, below is an example class State { public: //... int population() const; float aveTempF() const; //... }; struct PopLess : public std::binary_function<State,State,bool> { bool operator ()( const State &a, const State &b ) const { return popLess( a, b ); } }; sort( union, union+50, PopLess() ); Question : Now, How does the statement, sort(union, union+50,PopLess()) work? PopLess() must be resolved into something like PopLess tempObject.operator() which would be same as executing the operator () function on a temporary object. I see this as, passing the return value of overloaded operation i.e bool (as in my example) to sort algorithm. So then, How does sort function resolve the third parameter in this case? Question : 2 Question Do we derive any particular advantage of using function objects versus function pointer? If we use below function pointer will it derive any disavantage? inline bool popLess( const State &a, const State &b ) { return a.population() < b.population(); } std::sort( union, union+50, popLess ); // sort by population PS : Both the above references(including example) are from book "C++ Common Knowledge: Essential Intermediate Programming" by "Stephen C. Dewhurst". I was unable to decode the topic content, thus have posted for help. Thanks in advance for your help.

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  • Access cost of dynamically created objects with dynamically allocated members

    - by user343547
    I'm building an application which will have dynamic allocated objects of type A each with a dynamically allocated member (v) similar to the below class class A { int a; int b; int* v; }; where: The memory for v will be allocated in the constructor. v will be allocated once when an object of type A is created and will never need to be resized. The size of v will vary across all instances of A. The application will potentially have a huge number of such objects and mostly need to stream a large number of these objects through the CPU but only need to perform very simple computations on the members variables. Could having v dynamically allocated could mean that an instance of A and its member v are not located together in memory? What tools and techniques can be used to test if this fragmentation is a performance bottleneck? If such fragmentation is a performance issue, are there any techniques that could allow A and v to allocated in a continuous region of memory? Or are there any techniques to aid memory access such as pre-fetching scheme? for example get an object of type A operate on the other member variables whilst pre-fetching v. If the size of v or an acceptable maximum size could be known at compile time would replacing v with a fixed sized array like int v[max_length] lead to better performance? The target platforms are standard desktop machines with x86/AMD64 processors, Windows or Linux OSes and compiled using either GCC or MSVC compilers.

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  • How to keep track of objects for garbage collection

    - by Yman
    May I know what is the proper way to keep track of display objects created and hence allow me to remove it efficiently later, for garbage collection. For example: for(i=0; i<100; i++){ var dobj = new myClass(); //a sprite addChild(dobj); } From what i know, flash's garbage collection will only collect the objects without strong references and event listeners attached to it. Since the var dobj is strongly referenced to the new object created, I will have to "nullify" it too, am I correct? Should I create an array to keep track of all the objects created in the loop such as: var objectList:Array = new Array(); for(i=0; i<100; i++) { var dobj = new myClass(); //a sprite addChild(dobj); objectList.push(dobj); } //remove all children for each (var key in objectList) { removeChild(key as myClass); } Does this allow GC to collect it on sweep?

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  • How to merge objects in php ?

    - by The Devil
    Hey everybody, I'm currently re-writing a class which handles xml files. Depending on the xml file and it's structure I sometimes need to merge objects. Lets say once I have this: <page name="a title"/> And another time I have this: <page name="a title"> <permission>administrator</permission> </page> Before, I needed only the attributes from the "page" element. That's why a lot of my code expects an object containing only the attributes ($loadedXml-attributes()). Now there are xml files in which the <permission> element is required. I did manage to merge the objects (though not as I wanted) but I can't get to access one of them (most probably it's something I'm missing). To merge my objects I used this code: (object) array_merge( (array) $loadedXml->attributes(), (array) $loadedXml->children() ); This is what I get from print_r(): stdClass Object ( [@attributes] => Array ( [name] => a title ) [permission] => Array ( [0] => administrator ) ) So now my question is how to access the @attributes method ? Thanks in advance, The Devil

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  • C# - Advantages/Disadvantages of different implementations for Comparing Objects

    - by Kevin Crowell
    This questions involves 2 different implementations of essentially the same code. First, using delegate to create a Comparison method that can be used as a parameter when sorting a collection of objects: class Foo { public static Comparison<Foo> BarComparison = delegate(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); }; } I use the above when I want to have a way of sorting a collection of Foo objects in a different way than my CompareTo function offers. For example: List<Foo> fooList = new List<Foo>(); fooList.Sort(BarComparison); Second, using IComparer: public class BarComparer : IComparer<Foo> { public int Compare(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); } } I use the above when I want to do a binary search for a Foo object in a collection of Foo objects. For example: BarComparer comparer = new BarComparer(); List<Foo> fooList = new List<Foo>(); Foo foo = new Foo(); int index = fooList.BinarySearch(foo, comparer); My questions are: What are the advantages and disadvantages of each of these implementations? What are some more ways to take advantage of each of these implementations? Is there a way to combine these implementations in such a way that I do not need to duplicate the code? Can I achieve both a binary search and an alternative collection sort using only 1 of these methods?

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  • MVC2 Modelbinder for List of derived objects

    - by user250773
    I want a list of different (derived) object types working with the Default Modelbinder in Asp.net MVC 2. I have the following ViewModel: public class ItemFormModel { [Required(ErrorMessage = "Required Field")] public string Name { get; set; } public string Description { get; set; } [ScaffoldColumn(true)] //public List<Core.Object> Objects { get; set; } public ArrayList Objects { get; set; } } And the list contains objects of diffent derived types, e.g. public class TextObject : Core.Object { public string Text { get; set; } } public class BoolObject : Core.Object { public bool Value { get; set; } } It doesn't matter if I use the List or the ArrayList implementation, everything get's nicely scaffolded in the form, but the modelbinder doesn't resolve the derived object type properties for me when posting back to the ActionResult. What could be a good solution for the Viewmodel structure to get a list of different object types handled? Having an extra list for every object type (e.g. List, List etc.) seems to be not a good solution for me, since this is a lot of overhead both in building the viewmodel and mapping it back to the domain model. Thinking about the other approach of binding all properties in a custom model binder, how can I make use the data annotations approach here (validating required attributes etc.) without a lot of overhead?

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  • Diff/Merge functionality for objects (not files!)

    - by gehho
    I have a collection of objects of the same type, let's call it DataItem. The user can view and edit these items in an editor. It should also be possible to compare and merge different items, i.e. some sort of diff/merge for DataItem instances. The DIFF functionality should compare all (relevant) properties/fields of the items and detect possible differences. The MERGE functionality should then be able to merge two instances by applying selected differences to one of the items. For example (pseudo objects): DataItem1 { DataItem2 { Prop1 = 10 Prop1 = 10 Prop2 = 25 Prop2 = 13 Prop3 = 0 Prop3 = 5 Coll = { 7, 4, 8 } Coll = { 7, 4, 8, 12 } } } Now, the user should be provided with a list of differences (i.e. Prop2, Prop3, and Coll) and he should be able to select which differences he wants to eliminate by assigning the value from one item to the other. He should also be able to choose if he wants to assign the value from DataItem1 to DataItem2 or vice versa. Are there common practices which should be used to implement this functionality? Since the same editor should also provide undo/redo functionality (using the Command pattern), I was thinking about reusing the ICommand implementations because both scenarios basically handle with property assignments, collection changes, and so on... My idea was to create Difference objects with ICommand properties which can be used to perform a merge operation for this specific Difference. Btw: The programming language will be C# with .NET 3.5SP1/4.0. However, I think this is more of a language-independent question. Any design pattern/idea/whatsoever is welcome!

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  • Updating UI objects in windows forms

    - by P a u l
    Pre .net I was using MFC, ON_UPDATE_COMMAND_UI, and the CCmdUI class to update the state of my windows UI. From the older MFC/Win32 reference: Typically, menu items and toolbar buttons have more than one state. For example, a menu item is grayed (dimmed) if it is unavailable in the present context. Menu items can also be checked or unchecked. A toolbar button can also be disabled if unavailable, or it can be checked. Who updates the state of these items as program conditions change? Logically, if a menu item generates a command that is handled by, say, a document, it makes sense to have the document update the menu item. The document probably contains the information on which the update is based. If a command has multiple user-interface objects (perhaps a menu item and a toolbar button), both are routed to the same handler function. This encapsulates your user-interface update code for all of the equivalent user-interface objects in a single place. The framework provides a convenient interface for automatically updating user-interface objects. You can choose to do the updating in some other way, but the interface provided is efficient and easy to use. What is the guidance for .net Windows Forms? I am using an Application.Idle handler in the main form but am not sure this is the best way to do this. About the time I put all my UI updates in the Idle event handler my app started to show some performance problems, and I don't have the metrics to track this down yet. Not sure if it's related.

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  • Positioning objects in views during re-orientation in iPad

    - by Arni
    iPad Gurus: Apple wants us to support all orientations. I take that to mean that a particular layout should either rotate so that all objects are positioned relatively the same OR, if that doesn't look good, then they ought to be repositioned, OR two views ought to be designed and built. If I rely on the built-in rotation mechanism, the objects either get resized or they straddle the edge of the page in one orientation or the other, or they disappear from view altogether. I can't seem to find the right settings to get the objects to align clearly so they are seen in each orientation. Repositioning leads to a lot of if statements in the View Controller. So I don't think Apple had that in mind. I tried replacing views and even view controllers in "willRotateToInterfaceOrientation" method, but that either causes crashes or the portrait views end up in landscape unexpectedly and vv. Moreover, two view controllers means double the coding for the same view. There must be proper way to handle orientation changes, but I have searched the internet and documentation and sample code in vain for something that works. How is this done properly? Thanks!

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